Release-coatings, film- and sheetcasting bases for substrates



RELEASE-COATINGS,- FILM- AND SHEET- (IASTIN G BASES FOR SUBSTRATESArthur D. Jordan, In, Moorestowri, Nair, assiguo'r to Rohrn & HaasCompany, Philadelphia, Pa., :1 corporation of Delaware 1 No Drawing.Application December 12,- 1957 7 Serial No; 702,266 1 6 Claims. (or.117-155 This invention relates to the preparationv 'of coatin gs whichare particularly adapted to be ern'ployed in the- States Patent pendingapplication Serial No. 633,840, filed January.

It is known to form films, sheets, and other pellicular material, anorganosol containing a film-forming material, or a molten film-formingmaterial upon'a substrate from which the pellicule can be removed bystripping. For this purpose, the substrate may be a polished metalsurface such as a highly polished stainless steel or other metal surfacewhich is resistant to corrosion by the material being case. It is alsoknown to use such materials as cellophane (regeneratedcellulosefilm'),'or polyethtylene sheets or films as casting bases forcertain materials which do not tend to adhere to such materials. Therehave also been various proposalsto employ coated papers or coatedpaperboards for the purpose of providing a less expensive and moreeconomical film and sheet forming operation. However, therelease-coatings here tofore employed on such bases generally result inimparting a rather dull surface on the face of the film or sheet whichwas formed in contact with the releasecoatings.

It has now been discovered thatrelease-coatings can be prepared fromcertain compositions as herein defined; and that either highly glossy,smo othsurfaces or dull surfaces can be obtained on the face of thefilms and sheets formed in contact with such release-coatings. Thus, thepresent invention provides release coatings which may be applied to anytype of substrate whether of a rigid material such as any metal which iseither polished or unpolished, or of flexible materials such as those ofplastic materials including cellophane and polyethylene, or on suchporous substrates as leather, textiles, papers, and paperboards, andwhich are capable of producing films and sheets cast thereon whosesurfaces formed in contact with the release-coatings are either dull orof highly glossy character. I

The release-coatings of the presentinvention may be obtained from anaqueous coating composition in the form of an aqueous dispersion of (a)a Water-insoluble linear addition polymer having a T, as definedhereinbelow of not above30 C., such as from about 5,0 C. to +30 C., (b)certain salts 6f linear copolymers having low molecular weight, and (c)Zinc oxide.

The T value referred to is the transition temperature oi inflectiontemperature which is found byplotting the modulus of rigidity' againsttemperature. A convenient, method for determining modulus of rigidityand transition temperature is described by I. Williamson, BritishPlastics, 2 3, 87-90, 102 (September 1950).; The T value here used isthat determined at 300 kg./cm. V

The proportions of the copo lymer salt (component (11)) and theotherpolymer.(component.(a)) may generally be from l0' to 35 parts ofthe former to 90 to 65 parts'of the latter, depending upon theparticular components mixed. The amount of zinc oxide may be from about5 to,4'0'%, and is preferably about 10 to 20% on the weight of, thetotalpolymer solids of components (a) and (b) when a glossy surface isdesired on the stripped film. The use of higher proportions, such as 30to 40% produce s a dull surface on the stripped film.

The first-mentionedpolymer (component (a)) may contain a smallproportion of hydrophilic groupsup to abo'ut2.5% by weight thereof inthe polymer molecule, but it is preferred that the copolymer consistentirely of hydrophobicpolymer units. The aqueous dispersion of thiswater-insoluble linear addition polymer may be formed by conventionalemulsion polymerization or co polymeriz ation procedures, such as aredescribed in United'St ates aten 2,790,736, column 4, "lines 8 to 74(incorporated herein by reference), from a single monomer orfrom amixture of monomers which form homop'olyme rs or copolymers having a Twhich is not above 30? C. Monomers which form sufiiciently softhomopolymers include the acrylates of primary and secondary alcohols,such as thosehaving from 1 to 18 carbon atoms. Other monomers which formsufiiciently soft homopolymers include the methacrylates of alcoholshaving '5 to 18'carbo n atoms. I- Iomopolymers of any of 'these monomersor copolymers of a mixture of two or more of these monomers may beemployed for the purpose of producing water-insoluble linear additionpolymers for the aqueous coating c'ompositions of the present invention."Preferably, however, the methyl, ethyl, propyl, or butyl acrylates areemployed. Any of these monomers which form soft polymers may becopolymerized with such hardening comonomers as the lower alkyl methacrylates in which alkyl group may have from 1 to lcarbohs, namely themethyl, ethyl, propyl, and butyl methacrylates, styrene, acrylonitrile,methacrylonitrile, vinyl acetate, vinyl chloride, vinylidene chloride,and the like. The amount of hard comonomer that may be copolymerizedwith one of the soft monomers above depends upon the particular hard andsoft comonomers to be copolymerized. The following list gives, forseveral typical copolymer systems, approximately the maxi mum amount ofaparticular hard cornonomer that may be used with a particular softcomonomer to provide copolymers which have T, values of about 10 C; andlower. They are accordingly within the preferred range cited above andconsiderably more of the hard comonomer could be used to providecopolymers which are still within the maximum scope of the invention asdefined by the upper T limit of 30f C. For example, a copolym t r 64% byweight of ethyl acrylate and 36% of methyl rnethacrylate has a T valueof about 20 C.:

Methyl a'crylate 75, ethyl acrylate 25, Ethyl acrylate 76, methylrn'ethacrylate 24, Ethyl acrylate 78, styrene 22, V Ethylacrylate 7 8,'acrylonit'rile 22,

Ethyl acryla'te 20, butyl methacrylat'e n-Propyl acrylate 62, methylmethacrylate 38, n-Propyl acrylate' 72, acryrenitrtl 28, l Butylac'rylate 5 8, metliy1' manaayrrreaz, 3 Butylac'r'ylat 68, acry'n1t'ril'e'3' 2, 1 Butyl-acrylafe 10,15uty meflia rylateam I Butyl'acr'yla'te 57,1styrefie'*43. i' i Copolymers .of 35 to 65% by weight ofbutadiene with 65 to 35% respectively by weight of acrylonitrile orstyrene are also useful copolymers having T, values between 50 C. and+30 C." V l The emulsifiers or dispersing agents that may be used forpreparing the monomeric emulsions before polymerization or dispersionsof the polymer after polymerization may be anionic or non-ionic or amixture of nonionic type with an agent of anionic type. The amount ofemulsifier or dispersing agent may depend upon the particular monomericsystem, but in general is from /2 to 3% by weight of the monomersemplcyed.

Suitable anionic dispersing agents include the higher fatty alcoholsulfates, such as sodium lauryl sulfate, alkylaryl sulfonates, e.g.sodium or potassium isopropylbenzene sulfonates or isopropyl naphthalenesulfonates, alkali metal higher aryl sulfosuccinates, e.g. sodium octylsulfosuccinate, sodium N-methyl-N-palmitoyltaurate, sodium oleylisothionate, alkali metal salts of alkylarylpolyethoxyethanol sulfatesor ,sulfonates, e.g. sodium t-octylphenoxypolyethoxyethyl sulfate having1 to 5 oxyethylene units.

' Suitable non-ionic dispersing agents include the following:alkylphenoxypolyethoxyethanols having alkyl groups of about 7 to 18carbon atoms and 6 to 60 or more oxyethylene units, such asheptylphenoxypolyethoxyethanols, octylphenoxypolyethoxyethanols,methyloctylphenoxypolethoxyethanols, nonylphenoxypolyethoxyethanols,dodecylphenoxypolyethoxyethanols, and the like; polyethoxyethanolderivates of methylene-linked alkyl phenols; sulfur-containing agentssuch as those made by condensing 6 to 60 or more moles of ethylene oxidewith nonyl, dodecyl, tetradecyl, t-dodecyl, and the like mercaptans orwith alkylthiophenols having alkyl groups of 6 to carbon atoms; ethyleneoxide derivatives of longchained carboxylic acids, such as lauric,myristic, palmitic, oleic, and the like or mixtures of acids such asfound in tall oil containing 6 to 60 oxyethylene units per molecule;analogous ethylene oxide condensates of long-chained alcohols, such asoctyl, decyl, lauryl, or cetyl alcohols, ethylene oxide derivatives ofetherificd or esterified polyhydroxy compounds having a hydrophobichydrocarbon chain, such as sorbitan monostearate containing 6 to 60oxyethylene units; etc.; also ethylene oxide condensates of long-chainor. branched-chain amines, such as dodecylamine, hexadecylamine, andoctadecylamine, containing 6 to 60 oxyethylene groups, block copolymersof ethylene oxide and propylene oxide comprising a hydrophobic propyleneoxide section combined with one or more hydrophilic ethylene oxidesections.

Instead of using one of the anionic or non-ionic emulsifiers mentioned,the copolymer salt (component (12)) may be employed as the emulsifierfor the monomers in the emulsion copolymerization to form the aqueousdispersion of the water-insoluble copolymer (component (a)), or it maybe used as a dispersing agent for dispersing a finely divided polymer orcopolymer (component (a)) to form the aqueous dispersion thereof.

If the copolymer salt is used as the emulsifying or dispersing agent inthe preparation of the aqueous dispersion of component'(a), the amountused may be just sufficient to effect the emulsifying or dispersingactions required, in which event additional copolymer salt (component(b)) is added later to provide the proper relative proportions betweencomponents (a) and (b) as defined hereinxbove. On the other hand, thefull amount of the copolymer salt needed to form the proper proportionthereof in the finalaqueous dispersion may be initially introduced toserve as the emulsifying or dispersing agent.

When the aqueous dispersion of the water-insoluble linear additionpolymer (component (a)) is formed by means of one of the otheremulsifying agents, it is merely necessary to add to the aqueousdispersion of component (a), thereby obtained, the proper. proportion ofthe mer solids in water.

copolymer salt. The product is an essentially stable dispersion which isrelatively non-corrosive since it contains no strongly acid material,such as an acidic catalyst, commonly used in thermosetting aminoplastcompositions. The concentration may be from 5 to 70% solids.

Component (b) is an ammonium salt of a low molecular weight copolymerselected from the group consisting of 1) copolymers of 20 to 30% byweight of methacrylic acid with 80 to 70% respectively of methylmethacrylate having molecular weights from about 500 up to about 35,000,(2) copolymers of maleic anhydride with styrene in approximately 1 to 1molar ratio having molecular weights from about 500 to 100,000, and (3)copolymers of maleic anhydride with a branched-chain hydrocarbonselected from the group consisting of olefmes and unsaturated terpeneshaving 4 to 10 carbon atoms such copolymers having anaverage' molecularweight of about 500 to 5,000.

When component (b) is an ammonium salt of the methacrylic acidcopolymers, it may be the simple ammonium salt or a complex zincammonium salt obtained in the manner hereinafter described. Themethacrylic acid copolymers of low molecular weight within the rangesuitable for the present invention may be identified in terms of theirviscosities in the form of their simple neutral ammonium salt at aconcentration of.22% poly- These viscosities should be from 2 to 30poises. It is essential that the methacrylic acid copolymers do notcontain an amount of methacrylic acid salt units in excess of 30% byweight since the release-coatings obtained from the mixed polymercompositions using such salts become noticeably and objection- Rowlandpatent. Besides the use of the mercaptans ally water-sensitive. On theother hand, the use of methacrylic acid copolymers containing less than20% methacrylic acid salt units have the disadvantage of excessiveviscosity and accompanying difiiculties in the preparation of therelease-coatings. These methacrylic acid copolymer salts may be obtainedby naturalization with ammonium hydroxide to a pH of about 6.5 to 10 ofan equeous emulsion copolymer dispersion obtained by the emulsioncopolymerization in the presence of about 3 to 5%, based on the weightof monomers, of a chaintransfer agent of a mixture of 20 to 30% byweight of methacrylic acid and 70 to of methyl methacrylate.

Except for the inclusion of about 3 to 5% by weight, based on the weightof monomers, of a chain-transfer agent, the copolymer dispersion may bemade by any of the conventional emulsion polymerization procedures. Forexample, the polymerization procedures disclosed in the passage ofMcLaughlin et 211., United States Patent 2,790,736, column 4, lines 8 to74, may be employed provided the proportion of a chain-transfer agent orchain regulator just specified above be included within thepolymerization mixture in addition to the other ingredients. The passageof that patent just referred to is incorporated herein by reference. Thechain-transfer agents which serve to reduce the molecular weight of thepolymer obtained by the emulsion polymerization procedure in proportionto the amount of chain-transfer agents used may be any one of thefollowing: longchain alkyl mercaptans, e.g., t-dodecyl mercaptan,isopropanol, isobutanol, long-chain alcohols, e.g., lauryl alcohol,t-octyl alcohol, CCl C 01 and CBrCl The styrene-maleic anhydridecopolymers may be prepared by the process disclosed in Rowland UnitedStates Patent 2,606,891. The proportion of chain regulator may be from 1to 5% or more as. disclosed in the listed in the Rowland patent, theremay be employed instead any of the chain-transfer agents mentionedhereinabove for use in making the methacrylic acid copolymers.

A third class of copolymer salts are those that may be obtained bycopolymerization of maleic anhydride with olefines or terpenescontaining 4 to carbon atoms including isobutylene, isoamylene,branchedehain hexenes, diisobutylene of the formula I I i tripropylenesincluding branched-chain types. CH CH(CH )CH CH(CH )CH CH=CH and theterpenes may be dipentene, limonene, terpineol, and dicyclopentadiene.The copolymerization of maleic anhydride with these olefines andterpenes usually results in the production of low molecular weightpolymers so that, in general, it is unnecessary to employ chain-transferagents in order to produce copolymers having the molecular weight rangedesirable for the compositions of the present invention. Thesecopolymers may be prepared by the procedure described in H-anford UnitedStates Patent 2,378,629 and the procedures disclosed therein areincorporated herein by reference. In general, their preparation maybesummarized as being a bulk polymerization or solution polymerizationin an organic solvent such as xylene or dioxanein the presence of a freeradical initiator such as benzoyl peroxide, lauroyl' peroxide, cumenehydroperoxide, t-butyl perben'z oate. The usual procedures; forisolating the copolymer may be employed such as removal of the solventand monomer by distillation or separation 'of the copolymer, whenprecipitated, by filtration. 7. I 1

As stated before, the simple ammonium or complex zinc ammonium salts ofthe various copolymers may be employed. In the case of maleic acidcopolymers either with styrene, the olefines, or theterpenes,neutralization with ammonia at room temperature up to 50-to 70C. produces both ammonium salt groups and amide groups in proportionscorresponding substantially to the proportions in which such groups arepresent in the half-salt of the half-amide of the copolymer. Simpleammonium salts of the maleic anhydride' copolymers may also be used, andthese salts are obtained'by neutralization with ammonium hydroxide atelevated temperatures above 70C.

Both the simple ammonium salts and the maleamic acid salts such as thoseof the half-salt of the half-amide-ty'pe can be converted into a complexzinc ammonium type of salt in a manner described hereinafter; and it isto be understood that when reference is made to an ammonium salt of anyof the copolymers herein described, this is intended to embrace thesimple ammonium salt, the maleamic acid salt, as well as the complexzinc ammonium salt whether or not it is formed from "a'simple ammoniumsaltor a maleamic acid salt. i

The complex zinc ammonium salt may be obtained from the ammonium saltsof themaleic acid'copolymers or from the simple ammonium or male'amicacid salts of the maleic anhydride copolymers by adding ammoniumhydroxide to a solution of zinc acetate or other. water- 7 soluble zincsalt, "thereby initially precipitating zinc hydroxide, which isredissolved by the addition of more 'ammonium hydroxide, therebyproducing a solution of the zinc ammonium acetate or other complex zincammonium salt which is then added'to the aqueous dispersion of theammonium salt of the copolymer. The complex zinc ammonium salt of thecopolymer has the advantage that it produces a final coating having evengreater resistance to water than coatings'formed from the simpleammonium o-r amine salts thereof. The latter coatings, however, havegood water-resistance which is adequate for most purposes. Generally,the simple ammonium copolymer salts are preferred because of theirinexpensiveness.

Finely divided zinc oxide of 1 to 100 micron size, preferably of pigmentgrade, such as not over 40 to 50 micron size, may be suspended in theaqueous dispersions of the two polymers (Components (a) and (b)especially when the simple ammonium salt of component (b) is used. Itserves to cross-link the carboxykcontaining polymers on like drying,during which the ammonia is apparently replaced by the zinc ion.Thecomposition may be applied to the substrate to be coated in anysuitable manner, such as by a knife .coater or by dipping,roller-coating, spraying, brushing or the like. After application, it ismerely necessary to pass the coated substrate, such as the paper,through the normal drying equipment. The dispersed polymericmaterialscoalesce during the drying to form a clear continuous film, which ishighly glossy and resistant to water, to grease, and to blocking. Thecoating on thesubstrate obtained from the composition is essentially amix-v ture of the several components described hereinabove except thatthe copolymer salt groups are substantially converted into amide and/orimide form and zinc salt form as the result of the volatilization ofammonia and cross-linking with the zinc oxide with or' Without that ofany complex zinc ammonium salt used.

The use of zinc oxide has the remarkable characteristic of increasingthe temperature at which blocking occurs to a point above the charringtemperature ofpaper which 5 normal fashion and even from the othersystems of the present invention show little or no removal ofsuchemulsifiers from the integral coatings made with the systems of thepresent invention using zinc oxide in the proportions above. Thecoatings obtained with zinc oxide are e-specially valuable because oftheir high block-resistance and or other substrate carrying such acoating can be formed ina continuous band and a film-forming solution ordispersion in organic solvents or plasticizers of a vinyl or acrylicpolymer may be applied to the coated face of the base, dried, and fusedat elevated temperatures, such as up to 180 C. or more. The cooledcasting can then be stripped and a glossy face is obtained 'on the sideof the cast film or sheet which had previously been in contact with thecasting support when zinc oxide content is about 5 to 20% as statedhereinbefo-re. Previously used organosol-release coatings for paper andlike bases have generally produced dull surfaces on the face of the castfilm whichhad been in contact with the release-coatings or they have hadthe disadvantage of being water-sensitive or water-soluble. The coatingsof the present invention are insensitiveto moisture andgrease-resistant.

As indicated above, the coating composition formedof the aqueousdispersion of components (a), (b), and (c) in the proportions definedhereinabove may be applied to any substrate either of flexible'or rigidcharacter, such as of metal, wood, glass; cement, concrete, or stonewhether smooth and polished or unpolished. It may be applied to fibrousand non-fibrous substrates including those of textiles and variousplastic materials such as films and sheets of cellophane, polyethylene,nylon, especially that of the polyamide type,polyethyleneglycolterephthalate, and so on.

The fibrous substrates to which the compositions are applied in carryingout the present invention include covers or book pages.

The coatings may be applied to building construction papers and boards,such as the facing paper on plasterboard, .It may be used as arelease-coating on a paper to be used as a liner in a concrete moldingform or adapted to be used forcovering freshly-laid concrete roads.

The release-coatings of the present invention may be employed on thesurface ofthe backing strip, made either of paper or Holland cloth, forsupporting the adhesivecoated face of a pressure-sensitive tape that isto be stripped therefrom. Thus, this release-coating may be employed asaprotective interlayer between the strippable backing or facing and theadhesive surface of various types of. pressure-sensitive adhesive tapesincluding elec trical tapes and so on; This release-coating may also beused in strippable' films and papers of the photographic arts.

For many of these purposes, the non-blocking and marresistantcharacteristics of the coated products are quite important. Animportantadvantage is also the fact that no high temperatures are required, noris any acid catalyst required to convert the coated films intoWater-insoluble or non-blocking coatings. The use of the aqueousdispersions also avoids the danger of fire and the toxic efiects onoperators. It requires no equipment for solvent recovery.

In the following examples, which are illustrative of the presentinvention, the parts given are by weight unless otherwise indicated. Theheat-seal temperature referred to is the temperature'at which two coatedsheets first begin to show traces of sticking together sufficiently tomar the coating upon separation of the sheets.

Example 1 (a) An aqueous dispersion-is prepared containing 100 parts ofthe ammonium salt of a copolymer ofabout 87% ethyl acrylate, 10.5%methyl methacrylate, and 2.5%

itaconic acid in 116 parts of Water; 28 parts of zinc oxide.

(passing a 325 mesh screen) are dispersed in 28 parts of water with 0.06part of t-octylphenoxypolyethoxyethanol containing about 12 oxyethyleneunits, and 02 part of the ammonium salt of the approximately 121 moleratio copolymer of maleamic acid/diisobutylene copolymer. The zinc oxidedispersion is mixed into the copolymer dispersion with agitation. Then asolution in 142 parts of water of 40 parts of the ammonium salt of theapproximately lzl mole ratio copolymer of maleamic acid/diisobutylenecopolymer is mixed with agitation into the zinc oxide/copolymerdispersion. A chipboard coated with the composition and dried showed noblocking at 180 F. and 100% relative humidity when a plurality of thecoated boards. were stacked upon one another. under a weight of 2% lbs./sq. in. T he coated board showed a heat-seal temperature. of above 400F.

(b) An organosol composed of:

100 parts of polyvinyl chloride,

30 parts of dioctyl phthalate,

30 parts of'epoxidized soybean oil, 20 parts xylene, and

10 parts of methyl ethyl-ketone is cast on the coated face of the coatedpaper of part (a). It is dried by heating at 140 F. about ten minutes,and then heating at 350 F. about ten minutes to dry and fuse the vinylresin. It is cooled and stripped. The stripped film is tough. coherent,and glossy on both faces.

A 15% solution of a copolymer of 85% vinyl chloride and 15% vinylacetate is spread over the coated surface of the paper prepared in part(a) hereof. The cast film is dried ten minutes at 140 F., ten minutes at220 F. and cooled. On stripping, the self-supporting film obtained isglossy on both faces.

Example 2 A coating composition is prepared containing 100 parts of acopolymer of 87% by weight of ethyl acrylate, 10.5% by weight of methylmethacrylate, and 2.5% of itaconic acid, 40 parts by weight of theammonium salt obtained by a copolymerization procedure using about 3% ofa chain-transfer agent on the weight of the comonomers, and 28 parts ofzinc oxide. The viscosity of a 22% solids solution obtained by heatingat 105 C. for two hours the aqueous dispersion of the ammonium salt ofthe 1: 1 mole ratio styrene/maleamic acid copolymer is 7000 centipoisesindicative of a molecular weight of about 50,000 to 100,000. The solidsconcentration of the coating composition was about 22%, and it wasapplied to a chipboard and dried. An organosol of the compositiondescribed in part (b) of Example 1 was applied in the manner describedtherein. The film was easily stripped after fusion and had glossysurfaces on both sides.

Example 3 A release-coating was applied to chipboard as in Example 1except that the composition employed was a 22% solids composition in anaqueous medium, the solids being formed of 100 parts of a copolymer ofof ethyl acrylate and 20% of methyl methacrylate, 40 parts of theammonium salt of a copolymer of 27.5% by Weight of methacrylic acid with72.5% by. weight of methyl methacrylate formed by copolymerization atabout C. in the presence of about 3% by weight of bromotrichloromethaneas a chain-transfer agent, and 28 parts of zinc oxide. The organosoldescribed in part (b) of Example 1 was appliedto the coated chipboard inthe manner described in Example 1 (b). The film stripped therefrom wasextremely glossy on both faces.

It is to be understood that changes and variations may be made withoutdeparting from the spirit and scope of the invention as defined in-theappended claims.

I claim: V

1. As an article of manufacture, a solid substrate carrying on at leastone surface thereof, a coating comprising a mixture of (a) awater-insoluble linear addition polymer having a T value not over 30 C.,(b) an ammonium salt of a copolymer having a molecular Weight from about500 to 100,000 selected from the group consisting of (1) copolymers of20 to 30% by Weight of methacrylic acid and 70 to 80% by weight ofmethyl methacrylate which form ammonium salts having, at a concentrationof 22% in Water at room temperature, a viscosity between 2 and 30poises, (2) copolymers of styrene and maleic anhydride in approximately1:1 mole ratio, and (3') copolymers in approximately 1:1 mole ratio ofmaleic anhydride with a compound selected from the group consisting ofbranched-chain olefines having 4 to 10 carbon atoms and unsaturatedterpenes having 4 to 10 carbon atoms, and (c) zinc oxide, theproportions betweem a and (b) being 65 to parts by weight of (a) to. 10to 35 parts of (b) and the amount of (0) being from 5 to 40% based onthe total weight of (a) and (b).

2. An article as defined'in claim 1 in which the substrate is formedofpaper.

3. An article as defined in claim 1 in which the substrate isa'paperboard.

.4. As-an article of manufacture, a fibrous substrate having on at leastone surface thereof a coating comprising a mixture of (a) awater-insoluble linear addition polymer having a T ,value not over 30C., (b) an ammonium salt of an approximately 1:1 mole ratio copolymer ofmaleamic acid and diisobutylene, said salt having an average molecularweight ofabout 500 to 5,000, the proportions between (a) and (b) being65 to 90 parts of (a) with 10 to35'parts of (b) and (c) 5 to 40% byWeight of zinc oxide based on the total weight of (a) and'(b).

5. As an article of manufacture, a fibrous substrate having on at leastone surface-thereof a coating comprising a mixture of (a)awater-insoluble linear addition polymer having a T1 value'not'over 30C., (b) an ammonium salt of an approximately 1:1 mole ratio co- 9polymer of maleamic acid and styrene having an average molecular weightbetween about 500 and about 100,000, the proportions between (a) and (b)being 65 to 90 parts of (a) with 10 to parts of (b), and (c) 5 to byweight of zinc oxide based on the total weight of (a) 7 and (b).

6. As an article of manufacture, a fibrous substrate having on at leastone surface thereof a coating comprising a mixture of (a) awater-insoluble linear addition polymer having a T value not over 30 C.,(b) an ammonium salt of a copolymer of 20 to 30% by weight ofmethacrylic acid with to by weight of methyl methacrylate, said ammoniumsalt having, at a concentration of 22% in water at room temperature, aviscosity be- References Cited in the file of this patent UNITED STATESPATENTS 2,540,962 Puppolo Feb. 6,- 1951 2,566,244 Pinkney Aug. 28, 19512,597,087 Cowgill May 20, 1952 2,744,836 Schubert 'May 8, 1956 2,784,630Koprow Mar. 12, 1957

1. AS AN ARTICLE OF MANUFACTURE, A SOLID SUBSTRATE CARRYING ON AT LEASTONE SURFACE THEREOF, A COATING COMPRISING A MIXTURE OF (A) AWATER-INSOLUBLE LINEAR ADDITION POLYMER HAVING A T1 VALUE NOT OVER30*C., (B) AN AMMONIUM SALT OF A COPOLYMER HAVING A MOLECULAR WEIGHTFROM ABOUT 500 TO 100,000 SELECTED FROM THE GROUP CONSISTING OF (1)COPOLYMERS OF 20 TO 30% BY WEIGHT OF METHACRYLIC ACID AND 70 TO 80% BYWEIGHT OF METHYL METHACRYLATE WHICH FORM AMMONIUM SALTS HAVING, AT ACONCENTRATION OF 22% IN WATER AT ROOM TEMPERATURE, A VISCOSITY BETWEEN 2AND 30 POISES, (2) COPOLYMERS OF STYRENE AND MALEIC ANHYDRIDE INAPPROXIMATELY 1:1 MOLE RATIO, AND (3) COPOLYMERS IN APPROXIMATELY 1:1MOLE RATIO OF MALEIC ANHYDRIDE WITH A COMPOUND SELECTED FROM THE GROUPCONSISTING OF BRANCHED-CHAIN OLEFINES HAVING 4 TO 10 CARBON ATOMS ANDUNSATURATED TERPENES HAVING 4 TO 10 CARBON ATOMS, AND (C) ZINC OXIDE,THE PROPORTIONS BETWEEN (A) AND (B) BEING 65 TO 90 PARTS BY WEIGHT OF(A) TO 10 TO 35 PARTS OF (B) AND THE AMOUNT OF (C) BEING FROM 5 TO 40%BASED ON THE TOTAL WEIGHT OF (A) AND (B).